1. Field of the Invention
The present invention relates, generally, to a windshield wiper assembly and, more specifically to a beam blade wiper assembly having improved wind lift characteristics.
2. Description of the Related Art
Air foils have long been used in connection with wiper blades. At higher vehicular driving speeds, the wiper blade assemblies are subject to forces which can cause the blade assemblies to lift from the windshield of the vehicle. This phenomenon is sometimes referred to as xe2x80x9cwind lift.xe2x80x9d Wind lift can result in a decrease in the effectiveness of the wiper blade assembly to clean the windshield. Under certain circumstances, such as heavy rain, sleet or snow, wind lift can have a serious effect on traffic safety. Thus, for many years, air foils of various designs have been employed to combat the wind lift problem.
Generally speaking, air foils generate a pressure that forces the wiper blade assembly into contact with the windshield most notably at elevated driving speeds where wind lift can be extreme. An air foil is usually carried by the wiper blade assembly and functions to combat wind lift by creating a positive pressure forcing the wiper blade into engagement with the windshield at elevated and even conventional vehicular speeds. The air foil usually includes a gently curved foil which is outwardly concave relative to the wiper blade assembly and which faces the general direction of the movement of the vehicle. The foil extends axially along a substantial length of the blade assembly and generally between the primary lever and a point just above the spine of the wiper blade.
Windshield wipers, commonly referred to as xe2x80x9cbeam blades,xe2x80x9d are also known in the art and include a unitary backbone or xe2x80x9cbeamxe2x80x9d with a wiper blade connected thereto. Examples of such xe2x80x9cbeam bladexe2x80x9d type wiper assemblies are described in U.S. Pat. No. 5,325,564 issued Jul. 5, 1994 and U.S. Pat. No. 5,485,650 issued Jan. 23, 1996, both in the name of Swanepoel. This type of windshield wiper includes an single elongated, homogeneous strip forming a spring backbone or beam. The backbone has a connecting formation at a central position for connection to a reciprocating arm which applies a force and moves the backbone. The backbone is typically curved along a single plane which is the same plane of curvature of the windshield of the vehicle. The backbone of the wiper assembly is made from spring steel and tapers in width from its center towards its free ends or tips, along both longitudinal sides of the backbone. A wiper element is secured to the backbone and is centered along a centerline line at substantially equal distance to the longitudinal sides of the backbone. The thickness is also tapered from the center. Swanepoel teaches that the thickness and width of the backbone and its radius of curvature should be matched along the length of the backbone so that the backbone will provide a force per unit length distribution in a longitudinal direction which increases towards both tips of the windshield wiper when the windshield wiper is in use, pressed downward intermediate its ends onto a flat surface.
While beam blades enjoy lower profiles when compared with tournament style windshield wiper assemblies and therefore are not as prone to wind-lift, beam blade windshield wiper assemblies are not immune to this problem. In fact, airflow underneath the leading edge of the backbone which extends past the wiper blade can create a lift force greater than the opposing force created by the wiper assembly. The result is wiper blade wind lift at lower vehicle speeds.
While the windshield wiper assemblies known in the art provide significant advances in the related technology, there continues to be a need in the art for improvements in the windshield wiper systems which result in improved performance at variable vehicle speeds, and reduced wind lift with simplicity of parts and reduction in manufacturing costs.
The present invention overcomes the disadvantages of the related art in a beam blade windshield wiper assembly having an elongated backbone defining a median line extending along its longitudinal beam length between its first and second ends. The backbone includes an upper surface and a lower mounting surface as well as first and second sides extending between the upper and lower surfaces and the first and second longitudinal ends. The first side of the backbone defines a leading edge and the second side of the backbone defines a trailing edge. The assembly also includes a wiper element having a longitudinal centerline, said wiper element mounted to said backbone such that its longitudinal centerline is offset from said median line of said backbone in the direction of said leading edge.
One advantage of the present invention is that it provides a beam blade wiper assembly which has a low profile, is aesthetically pleasing and which has improved wind lift characteristics. More specifically, because the spine of the wiper element is mounted flush to the leading edge of the backbone, the lift force generated with respect to the beam blade windshield wiper assembly is reduced and thereby resists the effects of wind lift.